The Effect Of Angiotripsy Therapy On The Neovascularization In Vulnerable Plaques Induced By Smoking Combined With Balloon Injury And High Lipid Diet

BackgroundAtherosclerosis, a progressive chronic inflammatory disease, causesmyocardial infarction, stroke, and peripheral vascular obstruction. Moreover,Acute coronary syndrome (ACS) refers to a group of symptoms because of theobstruction of the coronary arteries which is caused by rupture or erosion of anunstable atherosclerotic plaque and acute thrombosis. Therefore, to understandthe mechanism of vulnerable plaque formation is the key to decrease themorbidity and mortality of ACS.Vulnerable plaques, which have a thin fibrous cap and a large lipid coreunder the cap, increase risk to rupture due to intraplaque haemorrhage and caprupture. These characteristics of unstable structure, increased hemodynamicstress and inflammation response make it prone to rupture. However, thedetailed mechanism of vulnerable plaques rupture is not clear. Nowadays, many studies demonstrated that the formation of microvessels in the vessel wall andplaques maybe contributed to the progression of atherosclerosis and vulnerableplaques rupture.Several non-invasive imaging techniques are available to detect theatherosclerotic plaques formation, including CT, MRI and PET. However, thereis not an optimal method can be preformed to image vulnerable plaques clearly.With the development of ultrasound contrast agents, contrast-enhancedultrasound imaging is a potential imaging techniques not only because of itshigh-spatial and-temporal resolution but also because of the clinic safety,repeatability and stability.MethodsPart1: Induction of unstable plaque by smoking combined with ballooninjury and high lipid dietVulnerable paques were induced by smoking combined with ballooninjury and high lipid diet. Briefly, sixty New Zealand white rabbits wererandomly divided into three groups: control group (N，n=20), balloon injuredgroup（B,n=20）and smoking group (S,n=20). Rabbits in B and S groups werefed with high fat diet for20weeks. Passive smoking was performed twice aday and1h each times. The levels of TG、TC、LDL、ox-LDL、hs-CRP、IL-8in serum were detected using ELISA kits after20weeks. Neovascularizationin unstable plaques was determinate by contrast enhanced ultrasound (CEU).Furthermore, the histological characteristic of unstable atherosclerotic plaqueswas observed by HE stain. Immunohistochemistry stain was performed to evaluate the infiltration of macrophage in unstable plaques.Part2: The effect of angiotripsy therapy on the stability of vulnerableplaquesAfter successful establishment of the ideal rabbit model of vulnerableplaques in Part1, we perform angiotripsy therapy to the rabbit with vulnerableplaques and observed the neovascularization in unstable plaques by CEU.Finally, the immunohistochemistry stain of CD31was performed to analysisthe microvessel in plaques quantitatively.ResultsPart1: Induction of unstable plaque by smoking combined withballoon injury and high lipid dietSmoking combined with balloon injury and high lipid diet induced moreplaques in group S (17/17,100%). Morever, the ratio of unstable plaque ingroup S was78.13%(25/32) more than that in group B (the ratio of plaques is77.8%, the ratio of unstable plaque is23.3%, p<0.05, vs. group B). However, ingroup N，no unstable atherosclerotic plaques were seen in19rabbits. The ratioof neovascularization in group S was significantly higher than that in controlgroup, even higher than that in groups B (p<0.05, vs. group B). Furthermore, theunstable plaque was more observed in group S than other groups by CEU, whichwere confirmed by HE stain (p<0.05, vs. group B).Part2: The effect of angiotripsy therapy on the stability of vulnerableplaquesCEU assay demonstrated that angiotripsy therapy significantly decreased the microvessels and the blood perfution in plaques. However, classicneovascularization was observed in plaques without angiotripsy therapy, whichwas confirmed by immunohistochemistry stain of CD31.Conclusions1. The model of typical atherosclerotic unstable plaque can be induced bysmoking combined with balloon injury and high lipid diet in rabbits.2. Passive smoking promotes atherosclerotic plaques formation, increasesthe neovascularization in artery wall and active the inflammation cells toinfiltrate into plaques, all of that contribute to the formation and rupture ofvulnerable plaques.3. Angiotripsy therapy is effective for decreasing neovascularization inplaques. Therefore, these datas demonstrated that angiotripsy may be a potentialtherapeutic strategy to hamper vulnerable plaques formation and even rupture.